SPATIAL TRANSCRIPTOMICS REVEALS TRANSLATIONAL AND INflAMMATORY CHANGES UPON ARGININE DEPRIVATION IN GLIOBLASTOMA

Abstract AIMS Glioblastoma is a primary brain malignancy with poor prognosis. The immunosuppressive microenvironment, molecular heterogeneity and the blood-brain barrier makes this tumour diffcult to treat. Targeted and immune therapies have shown limited success, highlighting the need for novel therapies. We previously demonstrated the effectiveness of arginine deprivation using ADI-PEG20 when combined with radiation. The aim of this study was to investigate transcriptomic changes initiated by ADI-PEG20 to potentiate the effects of radiation. METHOD To investigate this hypothesis, the CT2A syngeneic mouse model was used. To systemically deplete arginine, mice with brain tumours were treated with 5IU of ADI-PEG20 subcutaneously. Brains were harvested 6 days after treatment with ADI-PEG20 and analyzed by 10x Genomics Spatial Transcriptomics to investigate changes in the transcriptome. PartekFlow, GOFigure, PathfindR and EnrichR were used for bioinformatic analysis. RESULTS Arginine deprivation downregulated genes encoding ribosomal subunits. Gene Ontology and KEGG pathway analysis indicated an overall decrease in genes involved in transcription, translation and ribosomal biogenesis which were targets for the Myc transcription factor. Arginine Deprivation upregulated pro-inflammatory genes, including genes under the influence of IFN-y (GBPs and ISGs), indicating involvement of the STAT1 and NFkB transcription factors upon ADI-PEG20 administration. CONCLUSIONS Arginine deprivation reduced overall protein synthesis, conserving energy to favour translation and transcription of components of the pro-inflammatory immune response. Our study provides some insights into the mechanisms of action of ADI-PEG20 in enhancing the effects of standard of care for GBM.